General Description of Dynamic Channel Configuration Control _DCCC_ Algorithm

7/28/2019 General Description of Dynamic Channel Configuration Control _DCCC_ Algorithm

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General description of Dynamic Channel ConfigurationControl (DCCC) Algorithm

Table of contents

General description of Dynamic Channel Configuration Control (DCCC) Algorithm.................1

1. Introduction ...........................................................................................................................12. Glossary ................................................................................................................................1

2.1 Terms ...........................................................................................................................12.2 Acronyms and Abbreviations .......................................................................................2

3. Application ............................................................................................................................23.1 Availability ..................................................................................................................2

3.2 Benefit .........................................................................................................................23.3 Limitation and Restriction ............................................................................................2

4. Technical Description ............................................................................................................24.1 Procedure and Algorithm .............................................................................................2

4.2 Uplink DCCC ..............................................................................................................34.3 Downlink DCCC ..........................................................................................................3

4.4 UE State Transition ......................................................................................................45. Implementation .....................................................................................................................5

5.1 Parameter .....................................................................................................................55.2 Example diagram .........................................................................................................5

5.3 Messages ......................................................................................................................76. Notes ................................................................................................................................... 10

7. Reference Information ......................................................................................................... 10

1. IntroductionThe interactive or background service has its own particular characters. The traffic volume can vary

rapidly, sometimes the volume is huge and sometimes the volume is little. So, during an interactive or background

service connection, because of the above character, we should dynamic allocate the OVSF channel code resourceaccording the current volume. If the volume is huge, the more channel code resource is allocated, while the volume

is little, the less channel code is allocated. If there is no volume, the UE state can transit from CELL_DCH state to

CELL_FACH state and CELL_PCH/URA_PCH state.

2. Glossary

2.1 Terms

Best Effort: The Best Effort services indicate the interactive or background services.

OVSF code: The OVSF code is an Orthogonal Variable Spreading Factor code, it is used as the downlink channelcode. on the source traffic requirement (DCH user).

DCCC: Adjust the DCH rate based on the source traffic requirement (DCH user).

RRC State Control: Control the RRC state transition, different amount of resource is consumed in different state.

Request Rate: The maximum rate limit threshold that the code resources can be allocated.

DCCC threshold Rate: If the request rate is below than or equal to this rate, the located dynamic allocated dont

work.


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2.2 Acronyms and Abbreviations

BE Best Effort

DCCC Dynamic Channel Configuration Control

DL Downlink

OVSF Orthogonal Variable Spreading Factor

RAB Radio Access Bearer

RB Radio BearerRL Radio Link

RLC Radio Link Control

RNC Radio Network ControllerRRC Radio Resource Control

TFC Transport Format CombinationTFCS Transport Format Combination Set

TVM Traffic Volume Measurement

UE User Equipment

UL Uplink

UMTS Universal Mobile Telecommunications System

3. Application

3.1 Availability

This is an optional feature for Huawei UMTS RAN. This feature is available on BSC6800V100R002 and later

generic releases of the BSC 6800 system.

3.2 Benefit

Through the dynamic allocating channel resource, the system resources can be optimized. Because the OVSF code

is limited, the Iub and Iur band resource is limited, if the resource can be allocated by the actual traffic volume, the

channel code using rate can be enhanced, the more UE call can be admitted. Through the state transition, the UEstate can transmit from CELL_DCH to CELL_FACH and from CELL_FACH to CELL_PCH/URA_PCH, in the

CELL_FACH or CELL_PCH/URA_PCH state, the code resource can be saved and the UE battery consumption

can decrease.

3.3 Limitation and Restriction

The DCCC function is restricted by license. The RNC provides DCCCC function only when DYNAMIC

CHANNEL CONFIGURATION CONTROL license is purchased.

4. Technical Description

4.1 Procedure and Algorithm

The DCCC algorithm performs rate re-allocation for UEs having best effort (BE) services, (that is interactive and

background) which are in the CELL_DCH RRC state. The DCCC algorithm serves the following purposes: In the

uplink the data rate is modified according to the volume of traffic to be transmitted, this information is obtained

from traffic volume measurements (TVM) that are made by the UE. A TVM is triggered if the RLC buffer payload

rises above an upper threshold (event 4a) for a predefined time period. A TVM is also triggered if the RLC bufferpayload drops below a lower threshold (event 4b) for a predefined time period. In the downlink, the DCCC

requests a CDMA channel code which is commensurate with the volume of traffic that is being transmitted. In thisway, the DCCC algorithm makes efficient use of the code resource. In order to achieve this, the RNC makes traffic

volume measurements for the DL. A TVM is triggered if the RLC buffer payload rises above an upper threshold

(event 4a) for a predefined time period. A TVM is also triggered if the RLC buffer payload drops below a lower

threshold (event 4b) for a predefined time period. If a service request rate is below than or equal to a DCCC control

threshold, the dynamic allocated channel code resource algorithm dont work. The threshold can be configured.

DCCC algorithm can send the MEASURMENT CONTROL to configure the uplink TVM upper threshold and

TVM lower threshold.


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The UE can send the MEASUREMENT REPORT to report the Event 4a and Event 4b.

The downlink measure report is the same to uplink, but it is a inter primitive in UTRAN.

4.2 Uplink DCCC

The same to the downlink DCCC, the down limit threshold and the up limit threshold can also be configured to UE.

When the UE observes that the uplink Transport Channel Traffic Volume stays a certain time below the down limitthreshold (event 4b) or above the up limit threshold (event 4a), it can report to UTRAN and the UTRAN can

allocate the appropriate channel resource.

The example of triggered by an up limit threshold report (event 4a):

4.3 Downlink DCCC

Since downlink channelisation codes are a scarce resource a UE with a too high, allocated gross bit rate (low

spreading factor) must be reconfigured and use a more appropriate channelisation code (with higher spreadingfactor). While a UE with too low, allocated insufficient bit rate (higher spreading factor) must also be reconfigured

and use a more appropriate channelisation code (with lower spreading factor). This could be triggered by a down

limit threshold or an up limit threshold for the Transport Channel Traffic Volume and some inactivity timer, i.e.that the Transport Channel Traffic Volume stays a certain time below the down limit threshold (event 4b) , or

above the up limit threshold (event 4a). After the RB has been reconfigured some of the transport formats and

transport format combinations that require a new SF can be used.

The example of triggered by a down limit threshold (event 4b):


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The example of triggered by an up limit threshold (event 4a):

4.4 UE State Transition

The UE state transition algorithm perform the state transition, when the RRC is setup, the UE activity is observed,if the activity is lower, UE can transit from CELL_DCH state to CELL_FACH or from CELL_FACH toCELL_PCH/URA_PCH, while if the activity is higher, it can transit from CELL_PCH/URA_PCH to

CELL_FACH or from CELL_FACH to CELL_DCH. Figure below shows the RRC states and state transitions. If

the UE have the BE service and CS domain service at the same time, the state transition algorithm dont work.

- When the current state is CELL_DCH, the RNC will monitor the UE activity. An RNC timer is started if a

low activity report is received. The RNC then determines the maximum number of the low activity reports, if thenumber of the low activity reports exceed the maximum number, RNC will trigger the move to CELL_FACH from

CELL_DCH.

- The transition from CELL_FACH to CELL_PCH is the same as the transition from CELL_DCH to

CELL_FACH.

- In CELL_PCH state, an RNC timer is started to monitor the number of CELL UPDATE message (if the

cell reselection occurs, the UE will report the CELL UPDATE message), if the number exceeds a threshold, the UE

transits from CELL_PCH to URA_PCH. In CELL_PCH or URA_PCH state, the UE transits to the CELL_FACHstate when there is date needed to transfer or the UE is paged by UTRAN. In CELL_FACH state, when the uplink

or downlink TVM report (event 4a) is received by UTRAN, the UE transits to the CELL_DCH state.


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-

5. Implementation

5.1 Parameter

UlRateThresForDCCC: The DCCC algorithm capability may be very low for some Best Effort (BE) service withvery low applied maximum rate. The UL DCCC algorithm does not activate for the BE service whose applied

uplink maximum rate is smaller than or equal to the threshold. Default value: 64k.

DlRateThresForDCCC: The DCCC algorithm capability may be very low for some Best Effort (BE) service with

very low applied maximum rate. The DL DCCC algorithm does not activate for the BE service whose applieddownlink maximum rate is smaller than or equal to the threshold. Default value: 32k.

Event4AThd: Event 4A trigger threshold. Default value: 1024bytes.

Event4BThd: Event 4B trigger threshold. Default value: 64bytes.

DtoFStateTransTimer: This parameter is used to detect the stability of a UE in low activity state in CELL_DCH

state. Default value: 180s.

FtoDTVMthd: The parameter is used to define the traffic volume measurement threshold for event 4a when thestate transition form FACH to DCH will be triggered. Default value: 1024bytes.

FtoPStateTransTimer: This parameter is used to detect the stability of a UE in low activity state in CELL_FACHstate. Default value: 180s.

CellReselectTimer: This parameter is used to detect whether a UE is in the state of frequent cell reselection.

Default value: 180s.

CellReselectCounter: For a UE in CELL_PCH, if the number of cell reselections exceeds this parameter within the

[cell reselection timer], it can be considered that the UE is in the state of frequent cell reselection. Default value: 9

5.2 Example diagram


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Traffic volumein RLC buffer

Event 4B

threshold

Default:64 bytes

Event 4B

Event 4B time

to trigger

Default:

5 seconds

Event 4B Event 4B

Event 4B pending

time after trigger

Default:

16 seconds

DCH to FACHtransition timerDefault:

180 seconds

If number of 4B reports div

number of reports > Stateredund coef (Default: 80%)


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5.3 Messages

5.3.1 DCCC Algorithm in DCH stateProcess of Modifying Parameters TTI and TB Number of UU or IUB Interface at Uplink Direction

Relation Between TTI, TB Number and Transmission Rate

- TTI refers to transmission time interval.

- TB Number refers to the number of transmit blocks.- Transmission rate = TB Number * TB Size / TTI

For example,

4 * 336bit / 20ms = 67200bps

12 * 336bit / 10ms 403200bps

Choose Connection-oriented performance measurement > Configure uplink/downlink throughput and transmission

rate.


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5.3.2 UE State TransitionD2F F2CP (take uplink for example)

(1) Subscribe to BE service.(2) Send a RRC_MEAS_CTRL message.(3) Receive RRC_MEAS_RPRT messages.(4) Send a RRC_RB_RECFG message.(5) If the DCH is no more needed, RL of IUB interface is released.

F2D/CP2F/UP2F

(1) After the D2F F2CP process, receive a RRC_MEAS_RPRT.

(2) Send a RRC_RB_RECFG message.

(3) If the DCH is desirable, RL of IUB interface is established.The CP2UP is seldom in use.

Check State Transition ResultThe parameter RRC STATE INDICATOR in the RB_RECFG message indicates state transition result.


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5.3.3 Traffic volume reporting

Process of Traffic Measurement

Traffic Measurement Object: RLC Payload Buffer

Traffic Measurement Event 4A, 4B


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6. NotesSome UE, available currently on market dont support CELL_PCH and URA_PCH state.

7. Reference Information1) 3GPP, TS 25.331 "Radio Resource Control (RRC)

2) 3GPP, TR 25.922 "Radio Resource Management Strategies"

General Description of Dynamic Channel Configuration Control _DCCC_ Algorithm

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